Emergency alarm systems that transmit warning signals to a remote receptor are generally well known and useful for summoning assistance. Those of the type that are worn concealed on the body of a person and activated by unobvious body movement are often used to alert guards or law enforcement officers of apparent criminal activity, the system permitting a person to send warning signals without detection although under casual, or possibly intense, observation. Further, when the alarm transmission system is wholly portable and worn concealed on the body of the user, it is available for use at any location and does not restrict the user's mobility. In contrast to stationary installations which require manual operation of a switch or the like, such as might be used behind a counter in a store or bank, wholly portable systems concealed on the user's body are far more suitable for use by persons engaged in mobile security duties, such as security guards patrolling extensive premises and the like.
Portable alarm activating systems that are worn on the body and activated by such body movement as chest cavity expansion upon a large intake of air or arm movement, such as the devices disclosed in U.S. Pat. Nos. 2,135,476 and 3,440,635, have the disadvantageous features of requiring a possibly observable movement which could even be physically impossible in some circumstances, which movement is not so unrelated to normal activity to minimize the possibility of an unintentional false alarm transmission. False alarms of any type have a destructive impact on any emergency organization regardless of whether it is public service or a privately maintained operation. The assistance resources are activated for both true and false alarms, diluting these resources and/or requiring the maintenance of a far more extensive assistance operative than otherwise necessary. If false alarms occur with significant frequency, the performance of the assistance resources could well deteriorate as personnel react to an alarm half-heartedly, suspecting that their assistance will be unnecessary.
Public service organizations, such as fire departments and police emergency networks, must attempt to differentiate between true and false emergencies to the extent possible, and when not possible, respond to every alarm without cynicism if they are to provide the services needed by the community, even though many false alarms received are intentional pranks. In private organizations and security systems connected to public service systems such as law enforcement facilities, false alarms are most often unintentional triggering of alarm devices. Nonetheless the impact of such false alarms have a like destructive effect on assistance resources and may create a reluctance in public service system to permit a direct remote connection between them and private security alarms. Hence private organizations must then provide an intermediate support system to determine whether a given alarm from the field is true or false. Such intermediate support systems add to the cost of security maintenance and in situations requiring prompt intervention of public servants, such as police officers, unduly delay the required assistance.
The potential for unintentional transmission of false alarms is diminished with the use of alarm activating devices that are controlled by a body's voluntary movement of the type that is seldom, if ever, performed without forethought. Such a device, disclosed in U.S. Pat. No. 4,227,189, is one mounted on and worn behind a belt or similar structure and includes a switch held in the open, or off, position by the outward pressure of the body it is pressed against. Such pressure is removed by stomach muscle contraction, releasing pressure means, such as springs or the like, that move a first electric contact to a second electric contact thus closing an electrical circuit connected to an alarm transmitter, such as a radio transmitter. While this device significantly diminishes the possibility of unintentional generation of a false alarm signal, while providing a wholly portable, concealed alarm transmission system that is activated by movement not easily detectable by an observer and not normally restricted even if the body is physically bound or the person is under duress not to move, the potential for a false alarm is not reduced to zero. If for any reason the stomach muscles are contracted in the absence of a situation warranting an alarm, the circuit has been closed activating signal transmission. Further, although the device disclosed in U.S. Pat. No. 4,227,189 preferably includes a switching cord easily disengaged from the transmitter so that the activating switch can be rendered nonfunctional when a person is putting it on or taking it off, this disengagement could be overlooked, particularly when the device is being removed, and upon release of the outward pressure of the body on the device, the circuit closes and the transmitter is activated.
Hence it would be desirable to provide a means for preventing an alarm transmission system from transmitting a signal unintentionally, even if the system otherwise has a low potential for such error. It would be desirable to provide a means warning the user that a movement normally sufficient to initiate signal transmission has occurred and providing the user with a mechanism for disengaging the system prior to actual signal transmission. To maintain the secrecy of the device under emergency situations, such warning means must, like the device itself and the activating movement, be not readily detectable to an observer, while the disengagement mechanism, to be used when no emergency exists, need not be so concealed. Such means preferably should not obstruct or delay the transmission when needed.
In U.S. Pat. No. 4,157,540 there is disclosed a wireless alarm system having a portable wireless transmitter assembly, the components of which can be mounted on a belt. The assembly includes a normally-open contact switch closed upon stomach muscle distension. This assembly does include a warning means comprising an electromagnetic vibrator that imparts a tingling sensation to the wearer when activated. The vibrator may be connected to the activating switch directly or through a timer. In either of two embodiments upon switch closure the timer activates the vibrator and then, after a predetermined time period, the transmitter. Upon an unintentional activation, the user must interrupt the alarm sequence before transmitter activation. Hence to be effective in precluding false alarms there must be a sufficient time delay between vibrator activation and transmitter activation for the user to respond to the warning and take the action necessary to interrupt the sequence. This patent suggests a delay interval of five or ten seconds, and the smaller this safety interval, the less effective is the timer means in preventing false alarms. Inherent in such system, however, is the inability of the user to override the safety means and avoid the delay in signal transmission. Thus the speed at which an alarm can be sounded at a remote receptor has in part been sacrificed to provide a means for interrupting what otherwise would be false alarms. In many emergency situations, in particular life threatening situations, the addition of 5 or 10 seconds to the response time could be a critical deficiency in the security operation.
U.S. Pat. No. 4,300,129 discloses an alarm device mounted within a belt buckle that is activated by stomach distension, which movement pulls a sliding element out of a housing against opposing spring force. The sliding element has a series of detent notches along its side(s) that engage detent followers to restrict movement to a series of discrete legs as opposed to a continuous movement. In this patent a warning system is attributed to the element's movement from one notch to the other; such movement changes belt tension which, when noticed by the wearer, warns of the device's activation. Signal transmission occurs only upon the element reaching a predetermined notch; prior to that time the element can be reset back into its original position. In such a device the warning means, belt tension loosening, is not such a distinct or abrupt sensation as a vibrator or the like and hence could go unnoticed by the wearer, particularly if separated from the body with one or more layers of clothing, which would be normal for a belt worn in customary fashion, or if the user is distracted or subjected to vibration such as in or on a moving apparatus or vehicle. Moreover again if the device is set so as to sufficiently delay signal transmission to permit the sequence to be interrupted and the device reset, time delay between encountering an emergency and actual signal transmission is necessarily created.
It is an object of the present invention to provide a means that prevents transmission of an unintentional alarm signal with an alarm transmission system, particularly with an alarm transmission system of the type that is wholly portable and designed to be worn concealed on the body of the user. It is an object to provide such a means for such an alarm transmission system that is activated by body movement not easily detected by an observer and not normally restricted by physical means or duress. It is an object to provide such means that both warns a user of the initiation of the signal activation sequence and permits interruption thereof and resetting, while not unduly delaying the signal activation when the initiation was intentional. It is an object to provide such a means including a warning mechanism that could not normally go unnoticed by the user. These and other objects of the invention are described in more detail below.